ROllertest was a fork of Minetest that would track the latest Minetest master, with an aim to improve the Android gameplay experience among other things.
Since then, the Minetest Android app has been improved greatly (partially thanks to ROllertest) and many improvements are now available in upstream. ROllertest is now deprecated and isn't seeing any further updates, and you should use the official Minetest Android app available from Google Play, F-Droid or from GitHub.